Fuel injection pumps are commonly designed to have two stages, a preliminary stage for fuel intake and pressurization, and a secondary stage from which the fuel is injected to the engine. The injection stage of such a pump may comprise a plurality of reciprocating pistons which intermittently discharge the fuel from associated cylinders, in properly timed sequence.
A mechanism of this sort is described, for example, in Dilig U.S. Pat. No. 1,971,601, wherein vane and piston pumps are employed to provide the two-stage effect. Beaman et al U.S. Pat. Nos. 2,495,685, 2,604,047, and 2,608,158 are similar, and Fritz U.S. Pat. No. 2,591,533 utilizes gear and piston pumps to achieve such an effect in an oil burner unit. U.S. Pat. Nos. 3,331,327, 3,363,569, and 3,394,688, to Roosa, employ a vane pump in combination with a high pressure, reciprocating piston pump, and a centrifugal governor and timing cam arrangement is disclosed. Similar units are also described in McClocklin U.S. Pat. Nos. 4,105,369, and in Bessiere 3,016,838.
Injection pumps of the type hereinabove referred to utilize the fuel itself as the means by which the moving parts ar lubricated. While this is, of course, entirely feasible when a petroleum-based fuel is employed, attempt to use other fuels can introduce serious, and indeed insurmountable, problem in such a pump Thus, an inadequately lubricated pump will ultimately "freeze" and become inoperative.
Accordingly, it is a primary object of the present invention to provide a novel pump assembly in which the pumping section is segregated from the drive mechanism, thereby permitting independent lubrication of the latter and use of the pump for a relatively non-lubricating fuel.
It is a more specific object of the invention to provide a two-stage injection pump that is adapted for use to pump aqueous fuels for hydrogen powered systems.
It is another object of the invention to provide a pump assembly having the foregoing features and advantages, which assembly is relatively uncomplicated and inexpensive to manufacture, and is yet highly efficient and dependable in operation.
A further object of the invention is to provide such an
assembly having novel means for readily permitting adjustment of its timing to the ignition cycle of the engine with which it is employed.
A still further object of the invention is to provide such an assembly having novel throttling means for permitting automatic adjustment of the volume of fuel injected, in response to engine speed.